Over 50% of global energy demand is currently met by oil and gas production, but as reserves dwindle, new sources tend to be smaller, remote and in deeper water. Oil is typically extracted as multiphase flow, a mixture of oil, water and gas. Where production profitability is marginal, knowing flow rates of each of these components becomes critical, yet typical multiphase flow measurement systems have uncertainties of 20 % or more.

The intrinsic complexities and the absence of a traceable reference network capable of independently evaluating multiphase meters hindered industry efforts to reduce these uncertainties. To overcome this barrier, a test methodology and reliable reference measurements needed to be developed.

This project developed a harmonised approach to measuring flow with multi-flow meters. For the first time, an inter-comparison of a test method demonstrated very good agreement in test data at two multiphase flow laboratories.

The project:

• Developed a comparison procedure, independent of the type of multiphase flow meter.
• Developed a transfer standard, based on mass flow measurement, feeder pipe length and observation of flow pattern.
• Established and implemented a standard testing protocol, concluding that a 10-minute sampling time is sufficient.
• Developed a data comparison method, that combined facility and multiphase flow meter uncertainties, so facilities can be compared without explicit reference to the performance of the flowmeter deployed.
• Performed a successful inter-comparison between two test laboratories, in different countries, across a range of parameters.

Delivering impact
The findings of the inter-comparison procedure were used as the foundation of the first standard guidelines for multiphase flow measurement. The methodology was submitted as an ISO technical report on multiphase measurements (ISO/TR21354), resulting in the ISO/AWI 21354 standard Measurement of multiphase fluid flow, due to be published in January 2020.

This will expand the laboratory harmonisation network and provide confidence in the robustness and relevance of the methods deployed.

This approach to multiphase flow measurements is being applied to an enlarged network of laboratories, covering a wider range of flow conditions and multiphase meter types, in the follow-on EURAMET project Multiphase flow reference metrology.